Lectures 4 and 5 Flashcards
What is an epithelial junction?
How the epithelial cells attach to other cells, typically along the lateral border
How are epithelial junctions classified?
By their function
What are the 3 types of epithelial junctions?
Tight junctions, cytoskeletal linked junctions, and gap junctions
Describe tight junctions.
Connect the luminal surface and seal neighboring cells, forming a cicumferential belt. (like the plastic around a 6 pack of cans)
Describe cytoskeletal linked junctions.
bind cells together and to the basal lamina
What are the 3 types of cytoskeletal linked junctions?
Adherent junctions, desmosomes (macul adherens), and hemidesmosome
Describe adherent junctions.
forms a continuous adhesion belt near the apical surface, right below the tight junction
Which types of epithelial junctions form continuous loops around cells?
tight and adherent
What are cadherins?
plasma proteins that interact in the narrow space of an adherent juncion
What anchors proteins in adherent junctions?
intermediate filaments
What do the tight junction and adherent junction form together?
terminal bar
Describe desmosomes (macula adherens).
They do not encircle the cell, more of a “spot weld,” they have extracellular filaments that span further to anchor the membranes, and they don’t have to be near the lateral luminal surface
Which junction is the strongest?
desmosomes
Describe hemidesmosomes.
half a desmosome used to anchor to the basal lamina
Describe gap junctions.
Closely related membranes, but not fused, allowing low resistance channel of electrical and chemical communication
What are the two apical border modifications?
microvilli and cilia
What are finger-like projections on the cell surface?
microvilli
What are hair-like projections on the cell surface?
cilia
List the characteristics of microvilli.
actin filaments, short, numerous, increase surface area in absorptive epithelia, called the brush border or striated border, can be branched (uncommon, only in male repro tract)
List the characteristics of cilia.
bundled microtubules, bigger, stronger, used for movement, parallel so they can beat together and move fluid over the surface, found in respiratory and repro tracts
True or False:
Cells are commonly compartmentalized due to its surroundings, parts of the cell are only in one area.
true
Epithelial junctions: cell to cell direct contact
tight junctions
Epithelial junctions: junction with some filaments
adherent junctions
Epithelial junctions: junction with many, crossing filaments
desmosome
Epithelial junctions: junction that gets really close, but doesn’t actually touch
gap junction
Which junction types are found near the apical surface?
tight and adherent
Which junction appears really dark?
desmosome
Epithelial junctions: junction that is half crossing filaments, found on basal surface
hemidesomosome
What are specialized epithelial cells modified into secretory structures that produces a variety of products for extracellular use?
glands
What are the 2 ways to classify glands?
by the number of cells and the relationship to surround tissue
What are 2 ways to classify number of cells?
unicellular and multicellular
Describe unicellular glands
single secretory cell located in a non-secretory epithelium, scattered throught
What is the most common unicellular gland?
goblet cells
Where are goblet cells commonly found?
respiratory and GI tracts-they commonly secrete mucopolysaccharides
Describe multicellular glands
an accumulation of specialized secretory cells, most glands will be this type
What are the 2 relationships to surrounding tissue classifications?
endocrine glands and exocrine glands
Describe endocrine glands.
DUCTLESS glands, dense vascular network, may have irregular clumps of cells, or cords of cells, or hollow follicles
Describe exocrine glands.
DUCTS, maintain a communication, many different ways to classify
What are the 3 ways to classify exocrine glands?
morphology, type of secretion, mode of secretion
What are the 2 different types of morphology?
simple and compound
What morphology has ducts that don’t branch?
simple-usually microscopic and found within an organ
What morphology has ducts that branch elaborately?
compound-usually discrete anatomic structures or organs themesleves
What are the 4 types of secretion?
serous, mucous, mixed, and lipid
Which type of secretion has watery secretion, stains relatively dark, nuclei are rounded near the base, apex is filled with secretory granules?
serous
Which type of secretion has viscous secretion, nuclei flattened near the base, stains lightly?
mucous
Which type of secretion has a combination of serous and mucous secretions?
mixed
Which type of secretion has a lipid secretion?
lipid
Which type of lipid secretions appears white with nuclei pushed to the edge of the cell?
common adipocyte
Which type of lipid secretion appears as little white spots inside a fuscia stained cell?
multilocular
What are the 4 modes of secretion?
merocrine, apocrine, holocrine, and cytocrine
Describe merocrine secretion.
loses secretory product only by exocytosis, MOST COMMON
Describe apocrine secretion.
apical portion of the cell is lost, membrane bound droplets and thin rims of cytoplasm and plasma membrane is released
Describe holocrine secretion.
entire cell lost, extruded and constitutes the secretory product
Describe cytocrine secretion.
transfer the secretory product to another cell or sheds the whole viable cells
